In the oil and gas industry, environmental concerns have become increasingly important over the years. Typically, any combustible gases vented to the atmosphere from a well are burned in a flare stack or a flare pit built into the ground, both of which are permanently installed at the well site. As the combustible gases are often mixed with liquids, such as hydrocarbons and other contaminants, the use of conventional flare stacks or pits often risks ground contamination of the surrounding area, which produces a potentially environmentally hazardous situation.
For instance, the liquids may not be fully burned as they leave the flare tip of the flare stack or pit and, thus, these liquids may be sprayed onto the surrounding ground and area vegetation. Alternately, if the liquids are burned, contaminated combustion products may build up on the flare tip and on the surrounding ground, if the combustion products are released to the atmosphere. As well, if the liquids are ignited by the burner, flaming liquids may fall onto the installation, the well site or the surrounding area, thus creating a fire, explosion and general safety hazard for the environment and the well site installation and operators.
Further, the combustible gases to be burned by the flare stack or pit often include a combination of lighter combustible gases and heavier combustible gases. Many installations fail to take into account this composition of the combustible gases and therefore, there may be an incomplete combustion of all of the components of the combustible gases. This may result in either the release of some combustible gases to the atmosphere or a backup of the combustible gases in the system. As well, flaming liquids may fall back onto the unburned combustible gases and ignite them.
In response to some of these environmental and other concerns, the industry has produced flare tanks for flaring the gas. Specifically, the combustible gases are flared into a tank which is installed into the ground adjacent to the well. However, when using a flare tank, a secondary containment tank must also be installed under ground for collecting any liquids, transported with the gas, which are not burned by the flare. The permanent installation of a flare tank and a secondary containment tank at the well site may be a very costly solution to the ground contamination problem. In addition, circumstances may arise where a permanently installed flaring unit is either impractical or undesirable. Thus, a portable unit may be preferred.
A number of other apparatuses have attempted to address the environmental and safety concerns noted above in a number of different manners. Several of these apparatuses may be portable.
U.S. Pat. No. 5,380,195 issued Jan. 10, 1995 to Reid et al is directed at a safety flare which is designed to be portable by mounting it upon a skid assembly. The specific flaring unit includes a container which contains a burner that has a number of downwardly directed nozzles. The mixture of the combustible gases and the liquid is directed through the nozzles in the burner so that both the combustible gases and the liquid are burned. The waste materials from the burned liquids and combustible gases are intended to be contained within the container. Although this patent is directed at a portable unit which may inhibit the discharge of waste products to the atmosphere, it may not fully address the other environmental and safety concerns noted above. For instance, if the liquids are fully burned, the contaminated combustion products will likely build up on the downwardly directed nozzles resulting in an inefficient burning of the combustible gases and possible backup in the system. Further, the patent provides for the collection of any unburned liquids in the bottom of the container. If liquids collect in the bottom of the container, the potential exists for flaming liquids or combustion products to fall into these liquids resulting in a fire and explosion hazard. The explosion hazard is increased by the fact that the container for the flaring unit is enclosed.
U.S. Pat. No. 4,255,128 issued Mar. 10, 1981 to Straitz, III is also directed at a portable safety flare contained in a trailer bed. Straitz, III also does not discuss or provide for any separation of the liquid from the combustible gases prior to burning. Rather, the entire mixture is directed through a number of headers or horizontal pipes to a number of vertical stainless steel pipes which extend from the headers at right angles. The vertical stainless steel pipes have burner heads at their upper ends. If the liquid and the combustible gases are not separated in the headers, then the liquid is passed through the burner. If the liquid is fully burned, contaminated combustion products may build up on the burner resulting in incomplete burning of the combustible gases or backup in the headers. If the liquid is not fully burned, any liquid passing through the burners will likely fall into the trailer bed where it may be ignited by flaming liquids and combustion products passing out of the burners. Alternately, the design may permit only lighter combustible gases to rise within the vertical stainless steel pipes for burning by the burners. In this event, the liquid and heavier combustible gases may require draining from the headers. However, there is no discussion in Straitz, III regarding the storage of any liquid nor is there any discussion of the combustion of any heavier combustible gases which do not rise within the vertical stainless steel pipes.
U.S. Pat. No. 4,516,932 issued May 14, 1985 to Chaudot is directed at a safety system designed to eliminate liquids entrained or condensed in combustible gases. This system is not designed to be portable. Chaudot uses a complex series of separators to separate out the liquid in order to avoid condensation and fallout of liquid drops at the burner. Although the system separates out the liquids, it does not take into account the composition of the combustible gases, and specifically, the potential for the combustible gases to include a combination of lighter and heavier combustible gases. Thus, the use of this system may result in an incomplete combustion of all of the combustible gases.
Finally, Canadian Patent No. 1,253,427 issued May 2, 1989 to Quinnell is directed at a non-portable apparatus for igniting flare gas. Quinnell describes an inlet conduit for the mixture of the combustible gases and liquid which extends into a chamber and then bends upwardly in an elbow to form an upwardly projecting extension. The mixture in the inlet conduit is then caused to flow through laterally opening discharge apertures in the wall of the conduit. As a result, the mixture is directed out of the inlet conduit toward the interior wall of the chamber, causing at least some of the entrained liquid in the combustible gases to condense. Quinnell states that the combustible gases will flow upwards towards the igniter, while the liquids will flow downwards towards the lower end of the chamber. However, Quinnell does not take into account the composition of the combustible gases, and specifically, the likely inclusion of heavier combustible gases in the mixture. As a result, any heavier combustible gases may fall downwardly towards the lower end of the chamber with the liquids. Thus, only lighter combustible gases may rise within the chamber for combustion by the igniter.
Each of Reid, Straitz, Quinnell and Chaudot have only partially addressed the environmental and safety concerns noted above. Neither Reid nor Straitz, III appear to deal with any potential problems which may result from the passage of the liquid through the burner nor do they appear to take into account the composition of the combustible gases. As a result, both Reid and Straitz, III may result in a fire hazard and incomplete combustion of all of the components of the combustible gases. While Quinnell and Chaudot may provide for the separation of the liquid from the combustible gases prior to combustion, these apparatuses similarly appear not to take into account the components of the combustible gases and may therefore result in an incomplete combustion of all of the components of the combustible gases.
There is therefore a need in the industry for a method and a relatively simple apparatus for burning combustible gases contained in a mixture of the combustible gases and the liquid, in a relatively efficient, environmentally friendly and safe manner as compared to known apparatuses and methods. Further, there is a need for a method and an apparatus which separate the liquid from the combustible gases prior to the burning of the combustible gases and which take into account both the heavier and lighter components of the combustible gases in the combustion. Finally, there is a need for such an apparatus to be portable.